This invention relates to a method for the preparation of transparent electroconductive coatings on a transparent polymeric substrate.
Processes for the formation of conductive coatings on nonconductive substrates such as plastics are well known and used commercially, for example, in the production of low cost plastic articles that have a metal appearance. One such process is disclosed in U.S. Pat. No. 3,650,708, issued Mar. 21, 1972 to W. P. Gallagher. Such processes are commonly used for decorative or other purposes. A wide variety of commercially available opaque and transparent polymeric materials are used for this purpose. Considerable progress has been made with many of the available polymeric materials in producing adherent metal deposits thereon. The coating processes employed generally include a variety of substrate pretreatments including etching steps, and treatments with various conditioners and solvents. Typically, when such processes are applied to a polymeric substrate for decorative purposes, the clarity or transparency of the substrate or of the final plated article is of no consideration. However, for various purposes it is desirable to provide a transparent electroconductive coating on the surface of a clear transparent polymer material without appreciable loss of the clarity or transparency of the substrate. Transparent plastic materials having electroconductive transparent coating thereon are useful for a wide variety of commercial purposes, for example, in the construction of transparent electrodes, electroluminescent devices, liquid crystal display devices, electrooptical devices or materials and the like. Commonly, when known processes for the conductivizing of plastic materials are applied to clear transparent plastic materials, such as acrylates, such as polymethylmethacrylate or polymethylacrylate, or polyethylene terephthalate, the clarity or transparency of the material is adversely effected. Furthermore, although such materials may be conductivized by known techniques, when the materials are in the form of relatively thin substrates such as, sheets, films, or tape, the result of such flexing action frequently results in problems with respect to adherence of the metallic coating.
It is, therefore, an object of the present invention to provide an improved process for the preparation of a transparent electroconductive coating on polymeric substrates. It is a further object of the invention to provide a process for the production of adherent metallic coating on thin, transparent, flexible polymeric substrates such as polymeric films, sheets, tapes or the like. It is further object of the invention to provide a transparent polymeric material having a transparent electroductive coating thereon, suitable for use in the manufacture of electrooptical materials and devices such as transparent electrodes, electroluminescent devices, liquid crystal display devices, and the like.